This study is the earliest and perhaps the best study in this research area to date, as it was thoroughly placebo-controlled and showed dramatic contrast in response to hypnosis treatment above the placebo group. Thirty patients with severe symptoms unresponsive to other treatment were randomly chosen to receive 7 sessions of hypnotherapy (15 patients) or 7 sessions of psychotherapy

plus

placebo pills (15 patients). The psychotherapy group showed a small but significant improvement in abdominal pain and distension, and in general well-being but not bowel activity pattern. The hypnotherapy patients showed a dramatic improvement in all central symptom. The hypnotherapy group showed no relapses during the 3-month follow-up period.

Graph adapted from the above paper, showing group differences in two of the main IBS symptoms:

Whorwell PJ; Prior A; Colgan SM. Hypnotherapy in severe irritable bowel syndrome: further experience. Gut, 1987 Apr, 28:4, 423-5.
This report summed up further experience with 35 patients added to the 15 treated with hypnotherapy in the 1984 Lancet study. For the whole 50 patient group, success rate was 95% for classic IBS cases, but substantially less for IBS patients with atypical symptom picture or significant psychological problems. The report also observed that patients over age 50 seemed to have lower success rate from this treatment.

Harvey RF; Hinton RA; Gunary RM; Barry RE. Individual and group hypnotherapy in treatment of refractory irritable bowel syndrome. Lancet, 1989 Feb, 1:8635, 424-5.
This study employed a shorter hypnosis treatment course than other studies for IBS, and the success rate was lower, most likely demonstrating that a larger number of sessions is necessary for optimal benefit. Twenty out of 33 patients with refractory irritable bowel syndrome treated with four sessions of hypnotherapy in this study improved. Improvement was maintained at a 3-month treatment. These researchers further found that hypnosis treatment for IBS in groups of up to 8 patients seems as effective as individual therap

Prior A, Colgan SM, Whorwell PJ. Changes in rectal sensitivity after hypnotherapy in patients with irritable bowel syndrome. Gut 1990;31:896.
This study found IBS patients to be less sensitive to pain and other sensations induced via balloon inflation in their gut while they were under hypnosis. Sensitivity to some balloon-induced gut sensations (although not pain sensitivity) was reduced following a course of hypnosis treatment.

Houghton LA; Heyman DJ; Whorwell PJ. Symptomatology, quality of life and economic features of irritable bowel syndrome--the effect of
hypnotherapy. Aliment Pharmacol Ther, 1996 Feb, 10:1, 91-5.
This study compared 25 severe IBS patients treated with hypnosis to 25 patients with similar symptom severity treated with other methods, and demonstrated that in addition to significant improvement in all central IBS symptoms, hypnotherapy recipients had fewer visits to doctors, lost less time from work than the control group and rated their quality of life more improved. Those patients who had been unable to work prior to treatment resumed employment in the hypnotherapy group but not in the control group. The study quantifies the substantial economic benefits and improvement in health-related quality of life which result from hypnotherapy for IBS on top of clinical symptom improvement.

Koutsomanis D. Hypnoanalgesia in the irritable bowel syndrome. Gastroenterology 1997, 112, A764.
This French study showed less analgesic medication use required and less abdominal pain experienced by a group of 12 IBS patients after a course of 6-8 analgesia-oriented hypnosis sessions followed by 4 sessions of autogenic training. Patients were evaluated at 6-month and 12-month follow-up.

Houghton LA, Larder S, Lee R, Gonsalcorale WM, Whelan V, Randles J, Cooper P, Cruikshanks P, Miller V, Whorwell PJ. Gut focused hypnotherapy normalises rectal hypersensitivity in patients with irritable bowel syndrome (IBS). Gastroenterology 1999; 116: A1009.
Twenty-three patients each received 12 sessions of hypnotherapy. Significant improvement was seen in the severity and frequency of abdominal pain, bloating and satisfaction with bowel habit. A subset of the treated patients who were found to be unusually pain-sensitive in their intestines prior to treatment (as evidenced by balloon inflation tests) showed normalization of pain sensitivity, and this change correlated with their pain improvement following treatment. Such pain threshold change was not seen for the treated group as a whole.

Vidakovic Vukic M. Hypnotherapy in the treatment of irritable bowel syndrome: methods and results in Amsterdam. Scand J Gastroenterol Suppl, 1999, 230:49-51.Reports results of treatment of 27patients of gut-directed hypnotherapy tailored to each individual patient. All of the 24 who completed treatment were found to be improve.

Galovski TE; Blanchard EB. Appl Psychophysiol Biofeedback, 1998 Dec, 23:4, 219-32. Eleven patients completed hypnotherapy, with improvement reported for all central IBS symptoms, as well as improvement in anxiety. Six of the patients were a waiting-control group for comparison, and did not show such improvement while waiting for treatment.

Gonsalkorale WM, Houghton LA, Whorwell PJ. Hypnotherapy in irritable bowel syndrome: a large-scale audit of a clinical service with examination of factors influencing responsiveness. Am J Gastroenterol 2002 Apr;97(4):954-61.This study is notable as the largest case series of IBS patients treated with hypnosis and reported on to date. 250 unselected IBS patients were treated in a clinic in Manchester, England, using 12 sessions of hypnotherapy over a 3-month period plus home practice between sessions. Marked improvement was seen in all IBS symptoms (overall IBS severity was reduced by more than half on the average after treatment), quality of life, and anxiety and depression. All subgroups of patients appeared to do equally well except males with diarrhea, who improved far less than other patients for unknown reason.

Lea R, Houghton LA, Calvert EL, Larder S, Gonsalkorale WM, Whelan V, Randles J,
Cooper P, Cruickshanks P, Miller V, Whorwell PJ.Gut-focused hypnotherapy normalizes disordered rectal sensitivity in patients with irritable bowel syndrome.Alimentary Pharmacology& Therapeutics 2003 Mar 1;17(5):635-42.
This study evaluated the rectal sensitivity changes in IBS patients who received hypnotherapy, like a previous study by the same group (see Houghton et al's study above, but using a slightly different methodology. Twenty-three IBS patients were tested before and after 12 weeks of
hypnotherapy. Following the course of hypnotherapy, the mean pain sensory threshold increased in the hypersensitive subgroup and tended to decrease in the hyposensitive group,
although the l. Reduction in gut pain sensitivity was associated with a reduction in abdominal pain. These results suggest that hypnotherapy may work at least partly by normalizing bowel perception in those patients who have abnormal gut sensitivity, while leaving normal sensation unchanged.

Gonsalkorale WM, Miller V, Afzal A, Whorwell PJ. Long term benefits of hypnotherapy for irritable bowel syndrome. Gut. 2003 Nov;52(11):1623-9.
In this study, 204 IBS patients treated with a course of hypnotherapy completed questionnaires scoring symptoms, quality of life, anxiety, and depression before, immediately after, and up to six years following treatment. 71% of patients showed improvement in response to treatment initially, and of those, 81% were still improved years later, while most of the other 19% only reported slight worsening of symptoms. Quality of life and anxiety or depression scores were also still significantly improved at follow-up but showed some deterioration. Patients also reported fewer doctor visits rates and less medication use long-term after hypnosis treatment. These results indicate that for most patients the benefits from hypnotherapy last at least five years.

Barabasz A, Barabasz M. Effects of tailored and manualized hypnotic inductions for complicated irritable bowel syndrome patients. Int J Clin Exp Hypn. 2006 Jan;54(1):100-12.
This small clinical pilot study provided preliminary data on the effects of hypnotic inductions tailored to an irritable bowel syndrome patient in each session compared to Palsson's fully scripted (standardized) protocol. A total of eight IBS patients previously unresponsive to any treatment were assigned randomly to either the tailored or standardized induction condition. Other than pre-testing for hypnotizability, the procedure followed for the standardized group (four subjects) was exactly as prescribed by O. Palsson (1998). The same scripts were used for the other (tailored) group of four patients except that the inductions were individualized. Patients showed favorable treatment response immediately post-treatment and at 10-month follow-up. Only the tailored group showed no incapacitating pain at post-treatment but greater emotional stress than the standardized group. The tailored group continued to improve and showed better results than the standardized group at 10-month follow-up, and the post-reatment emotional distress had decreased significantly

Smith GD. Effect of nurse-led gut-directed hypnotherapy upon health-related quality of life in patients with irritable bowel syndrome. J Clin Nurs. 2006 Jun;15(6):678-84.
This study conducted in Edinburgh, UK, measured the effects of a nurse-led gut-directed hypnotherapy. Seventy-five patients were treated with 5 to 7 1/2 hours of hypnotherapy, as well as receiving education and support. Diary results showed that the physical symptoms of abdominal pain and bloating improved significantly after treatment. There were also significant statistical improvements in six of the eight health-related quality of life scales and in anxiety scores after treatment.
Vlieger AM, Menko-Frankenhuis C, Wolfkamp SC, Tromp E, Benninga MA. Hypnotherapy for children with functional abdominal pain or irritable bowel syndrome: a randomized controlled trial. Gastroenterology. 2007 Nov;133(5):1430-6.
This randomized controlled trial compared the effectiveness of six sessions of hypnotherapy over 12 weeks with results from standard medical therapy plus six sessions of supportive therapy in children with functional abdominal pain or IBS. Fifty-three children ranging in age from 8 to 18 years, with functional abdominal pain (31patients) or IBS (22 patients), were randomly assigned to either hypnotherapy or the comparison treatment. Pain scores decreased significantly in both groups from baseline to 1 year follow-up, but the hypnotherapy group showed significantly greater reduction in pain compared with the comparison group. At one-year follow-up, treatment was judged successful for 85% of the hypnotherapy group and 25% of the comparison group (p< .001).